The neuropathological examination of the brain provides essential information about factors contributing to clinical symptoms and to anatomical, cellular or biochemical data that might be extracted from it. The neuropathological evaluation is reliable for characterizing the type, extent and location of any visible lesion or the absence of visible abnormality. The neuropathology core must provide information about specimens made available to research in a systematic and reliable fashion, while meeting the specific needs of investigators. The specimens must be optimally categorized and prepared for research. Furthermore Core B assists investigators in evaluating tissue sections and in correlating their findings with those observed with conventional means of neuropathological studies. The specific aims of the neuropathology core are: 1. to organize for the Center the availability, storage and distribution of brains and samples of peripheral tissues from patients who have died with the clinical diagnosis of Huntington disease (HD) and from patients without neurologic or psychiatric disorders, 2) to provide standardized pathologic assessment and diagnoses for the brains and tissues collected; and select the brains and peripheral tissue samples that are suitable for collecting normal data for comparative studies, 3) to categorize the HD brains i one of five (0-4) grades according to the extent of the neuropathological changes, 4) to prepare brains and peripheral tissue samples according to two protocols that lead to standardized tissue preparation for research and reduce variable impairing interpretation and comparison of data, 5) to perform autopsies of HD patients who have died within the greater Boston area but outside the Massachusetts General Hospital (MGH) to harvest brains and organs as soon as possible after death, and 6) to build up a systematically selected library of paraffin embedded tissue and slides that have been obtained from HD brains, from brains with degenerative changes involving the basal ganglia, other than HD; and from normal brains; these blocks constitute nucleic acid repository with specific anatomical origins; the slides are essential for quantitative or comparative studies. The core will provide tissue for all 4 Projects.